It is well known by biologists and fishermen that water temperature exerts a strong influence on the ranging and feeding habits of fresh and salt water game fish and that a given species of fish will tend to be found most frequently in a body of water characterized by a fairly narrow temperature range. Thus, there exists a wide variety of devices used to position fishing baits at various water depths ranging from the simple lead weight to fairly elaborate trolling devices incorporating heavy weights with remote sensing devices attached. The simple sinker provides no indication of temperature and the latter devices are both costly and cumbersome.